Is there any way to fetch the Bisq Price Index data programmatically outside of Bisq through a REST API or similar (without running an actual Bisq Price Node)? Or do we have to fetch it from all the different sources and calculate it ourselves? Is that basically what a Price Node does?
Not sure about the answer to your question but here is some info from the wiki that might be useful if you have not seen them:
I think those links are outdated as they describe the old BitcoinAverage method of getting the price that Bisq used. I believe these days the Bisq Price is calculated as an average of the current price of different exchanges.
I think you are correct that the info is outdated. You could try asking in the #ops channel in Keybase. They might have more info.